Bearing arrangement for a turbocharger, and turbocharger

ABSTRACT

A bearing arrangement for a turbocharger, including a bearing housing-which extends in an axial direction, an anti-friction bearing, situated within the bearing housing, having an outer bearing ring and a number of rolling bodies and an axially extending shaft which is rotatably mounted within the bearing housing. It is provided that the shaft includes a rolling body raceway for guiding the rolling bodies. Moreover, the invention relates to a turbocharger having such a bearing arrangement. A bearing arrangement of this type allows the secure mounting of a shaft in a turbocharger with simple assembly and low costs.

The present invention relates to a bearing arrangement for a turbocharger, including a bearing housing, an anti-friction bearing, situated within the bearing housing, having an outer bearing ring and a number of rolling bodies, and an axially extending shaft which is rotatably mounted within the bearing housing.

Moreover, the present invention relates to a turbocharger having an above-mentioned bearing arrangement.

BACKGROUND

A turbocharger is usually used for increasing the power of internal combustion engines by utilizing exhaust gas energy. For this purpose, the turbocharger is composed of a compressor and a turbine which are connected to one another via a shaft mounted within a bearing housing.

During operation, the turbine is set into rotation by an exhaust gas flow, and via the shaft drives the compressor, which draws in and compresses air. The compressed air is led into the engine, a large quantity of air entering into the cylinders during the induction stroke due to the increased pressure. As a result, the oxygen content required for the combustion of fuel correspondingly increases, so that more oxygen enters into the combustion chamber of the engine with each intake stroke.

This results in an increase in the maximum torque, causing the power output, i.e., the maximum power at a constant working volume, to increase. This increase allows in particular the use of a more powerful engine having approximately the same dimensions, or alternatively, allows a reduction in the engine dimensions, i.e., achieving comparable power with smaller and lighter machines.

Since the shaft rotates at a high rotational speed during operation of a turbocharger, the shaft must be securely mounted to allow problem-free operation of the turbocharger.

A bearing unit, designed as a bearing mounting system, for a turbocharger of the type mentioned at the outset is known from DE 689 08 244 T2. A shaft is situated within a bearing housing. The bearing of the shaft within the bearing housing occurs via a pair of anti-friction bearings designed as ball bearings. The ball bearings in each case are composed of an outer bearing ring and an inner bearing ring, the inner bearing rings being fixedly fastened to the shaft.

SUMMARY OF THE INVENTION

Due to the above-mentioned configuration, a shaft of a turbocharger may be securely mounted, even at increased rotational speeds of the shaft. However, the use of a plurality of required separate bearing components and the associated high assembly cost do not represent a long-term solution for a bearing arrangement or a turbocharger.

A first object of the present invention is to provide a bearing arrangement which is improved over the related art, and which allows the secure bearing of a shaft in a turbocharger with simple assembly and low costs.

A second object of the present invention is to provide a turbocharger having such a bearing arrangement.

The present invention provides a bearing arrangement for a turbocharger, including a bearing housing which extends in an axial direction, an anti-friction bearing, situated within the bearing housing, having an outer bearing ring and a number of rolling bodies, and an axially extending shaft which is rotatably mounted within the bearing housing. It is provided that the shaft includes a rolling body raceway for guiding the rolling bodies.

The present invention takes into account the fact that there is concern for increased assembly effort as well as impairment of the bearing components, and thus of the function of the turbocharger, as the result of using a plurality of separate bearing components. This is particularly true with regard to the inner bearing rings that are usually used, which have corresponding raceways at their outer periphery for guiding rolling bodies. During assembly, the inner bearing rings are pushed onto the shaft, and must be pressed onto the shaft so that no twisting relative to the shaft is possible during operation. During the pressing, the bearing rings are compressed in such a way that the axial distance between the rolling body raceways is reduced, and thus the shaft play is changed. In addition, the diameters of the rolling body raceways, and thus also the bearing play, change.

In addition, pressing the inner bearing rings may result in misalignment of same on the shaft. For example, it is possible that the inner bearing rings are not coaxially aligned with the shaft and with one another, which may result in undesirable seating at the axial contact points between the bearing rings or the bearing seats during balancing as well as during subsequent operation. Furthermore, the balance quality may deteriorate over the running time of the bearing, resulting in increased wear of the bearing components. In any case, it is thus not possible to ensure problem-free functioning of a turbocharger.

Lastly, the present invention recognizes that the above-mentioned problems may surprisingly be overcome when the shaft includes a rolling body raceway for guiding the rolling body. The use of inner bearing rings to be separately installed may be dispensed with entirely. In other words, the shaft itself takes over the function of the inner bearing rings, so that a secure bearing of the shaft in a turbocharger may be achieved by this type of configuration at low cost and with ease of assembly.

In addition, the sum of the component tolerances may be reduced by dispensing with separate inner bearing rings. The usually additive shape and position defects of the inner bearing rings on the shaft may thus be avoided, so that the overall tolerance is smaller.

The shaft may be made of various materials, heat- and corrosion-resistant materials being particularly suited. The shaft may be manufactured in one piece, for example, with the aid of a shaping process, a machining process, or a casting process. As an alternative to the one-piece manufacture, multi-part manufacture is possible. The rolling body raceway is integrated into the lateral surface of the shaft, and may, for example, be introduced directly into the lateral surface in one step during manufacture of the shaft. Alternatively, the rolling body raceway may be subsequently introduced into the lateral surface in a step following the manufacture of the shaft base body. To ensure the necessary stability of the shaft, the shaft preferably undergoes a finishing operation after manufacture.

The shaft is rotatably mounted within a bearing housing in the installed state. For this purpose, the bearing housing preferably has a hollow cylindrical design. Due to the high stresses during operation of a turbocharger, in particular heat- and corrosion-resistant metallic materials are suited for manufacturing the bearing housing. The bearing housing is in particular provided with a location hole for the further components of the bearing arrangement such as the anti-friction bearing.

The anti-friction bearing and the individual anti-friction bearing components are also advantageously made of heat- and corrosion-resistant materials, for example through-hardened steels or also ceramics. The common types of bearings, for example cylindrical roller bearings or also tapered roller bearings, are basically usable as anti-friction bearings. Ball bearings, such as double-row angular-contact ball bearings in particular, are particularly suited. Two rolling body raceways situated at an axial distance from one another are advantageously introduced into the lateral surface of the shaft for guiding the rolling bodies of a double-row angular-contact ball bearing.

The anti-friction bearing is also provided with at least one outer bearing ring, on the inner periphery of which a rolling body raceway is introduced, which likewise is used for guiding and positioning the rolling bodies. In this regard, one-piece as well as multi-piece manufacture of the outer bearing ring is possible. For multi-piece manufacture, the outer bearing rings may, for example, abut one another, thus preventing axial displacement of the bearings on the shaft. Alternatively, the outer bearing rings may be situated at an axial distance from one another with the aid of a spring element, for example.

In particular a space, for example as a gap which surrounds the outer bearing ring, for a so-called quenching oil film is provided between the outer diameter of the outer bearing ring and the inner periphery of the bearing housing. In this case, the quenching oil film takes over the function of the vibration damper and prevents undesirable contact between the outer bearing ring and the bearing housing.

To supply the space with oil, a number of supply holes may be introduced within the bearing housing, via which oil may be metered from the engine oil circuit into the space. For this purpose, the supply holes are in communicating connection with a number of the grooves surrounding the outer periphery of the outer bearing ring. Similarly, the grooves may be acted on by oil via the supply holes. Starting from the grooves, the oil may be distributed over the periphery of the outer bearing ring in the axial direction, so that a uniform oil film forms between the outer bearing ring and the inner wall of the bearing housing. The number of supply holes and of the grooves is unlimited in principle, and may be adapted, for example, to the dimensions of the bearing housing and the thickness of the quenching oil film.

Furthermore, an outlet hole which is in communicating connection with a drainage groove which surrounds the outer bearing ring on its outer periphery is preferably additionally introduced into the bearing housing. It is thus ensured that the oil supplied to the space via the supply hole may continuously drain off

Alternatively, the outer bearing rings may be guided in the bearing housing via an additional support ring. In this case, the support ring is embedded in the space. The support ring preferably has a number of circumferential grooves on its outer periphery, which in the installed state are in communicating connection with the supply holes in the bearing housing. The quenching oil film is then correspondingly provided in the space between the outer periphery of the support ring and the inner wall of the bearing housing. When a support ring is used, a drainage groove which is introduced into the support ring on its outer periphery is advantageously in communicating connection with an outlet hole, and appropriately allows oil drainage.

Securing elements may be used to position the anti-friction bearing within the bearing housing with anti-twist protection. In principle, a plurality of securing elements is conceivable which withstand the forces acting during operation of a turbocharger and which allow an arrangement of the outer bearing ring within the bearing housing with anti-twist protection. The securing elements, the number of which is not limited in principle, may be designed, for example, as securing pins or securing bolts which may be inserted into holes provided for this purpose within the bearing housing. Alternatively, the securing elements may be designed as springs which may engage with depressions or grooves provided for this purpose.

In one advantageous embodiment of the present invention, the shaft, at least in the area of the rolling body raceway, is made of a steel. In principle, various steels or metallic materials are usable here. An alloyed anti-friction bearing steel is particularly suited. For example, an anti-friction bearing steel of type 81MoCrV42-16 may be used, which in particular due to its heat stability and corrosion resistance meets the necessary requirements for use in turbochargers. The properties of the metallic material or of the anti-friction bearing steel may be influenced by the selection of the alloy components or by the composition. In principle, it is possible to produce the entire shaft from an anti-friction bearing steel. Alternatively, an anti-friction bearing steel may be used only at the locations of the rolling body raceways.

In another advantageous embodiment of the present invention, the shaft is composed of a number of axially adjacent shaft sections. The individual shaft sections may be welded together prior to assembly of the bearing arrangement. The multi-piece configuration allows, for example, the controlled introduction of recesses into the shaft. These recesses provide an air volume within the shaft, which in the installed state of the shaft in the turbocharger reduces the thermal conduction from the turbine wheel to the anti-friction bearing.

The costs for manufacturing the shaft and for manufacturing the bearing arrangement may be reduced in particular by using multiple shaft sections. This is made possible in particular in that the shaft sections may be made of various materials. The shaft sections into which the rolling body raceways are introduced are preferably made of an anti-friction bearing steel which has the required stability. Requirement-specific material, and accordingly less expensive shaft material, may be used for the further shaft sections.

The shaft sections are preferably joined to one another by welding. Welding processes are particularly suited in this regard, since their use provides the option of also joining materials having different physical properties, for example joining steel to aluminum.

The shaft preferably includes an inner recess. The inner recess may be designed as a cavity which provides an additional air volume. For example, the thermal conduction from the turbine wheel to the bearing may be reduced in this way. In addition, the recess may be used for accommodating a so-called welding discharge which arises during the joining of the shaft to the turbine wheel or also during the joining of multiple shaft sections to one another, and which may then become caught within the recesses. In principle, a recess may also be introduced into the turbine wheel. The same applies to a multi-piece configuration of the shaft for the individual shaft sections, which likewise may each be provided with a recess. This further increases the interior air volume and further reduces the thermal conductivity.

The shaft preferably has a shaft journal on the end-face side for centering and fastening to a turbine wheel. The shaft journal is preferably designed as a journal which extends in the axial direction, and which in the installed state may engage with the hole in a turbine wheel. Thus, a connection between the components is possible even before the components are welded, which simplifies the subsequent welding process. In principle, providing a journal on the turbine wheel is also possible, in which case the journal engages with a hole at the end face of the shaft.

It is also possible in principle to introduce a recess into the journal which provides an air volume within the shaft. The thermal conduction from the turbine wheel to the anti-friction bearing may thus also be reduced with the aid of the journal.

The outer bearing ring advantageously includes a splash oil hole for acting on the anti-friction bearing with lubricant. The splash oil holes are connected to the grooves in the outer ring. The oil may pass from the grooves into the bearing space via the splash oil holes, thus being utilized for lubrication and cooling.

The shaft also preferably includes a number of grooves on its outer periphery for positioning sealing elements. The grooves may be introduced into the outer periphery of the shaft on the compressor side as well as on the turbine side, thus achieving a sealing effect on both sides of the shaft. The required lubrication of the anti-friction bearing positioned within the bearing housing, which is achieved via splash oil holes, for example, may be ensured in this way.

The shaft also preferably includes an oil separator. The oil separator may, for example, be mounted on the shaft as a separate component, or also integrated into the shaft. In particular, the oil separator is designed as an oil separator which operates by making use of the centrifugal force principle.

The second object of the present invention is achieved according to the present invention by a turbocharger, including a compressor wheel, a turbine wheel, and a bearing arrangement corresponding to the above-mentioned embodiments, the compressor wheel and the turbine wheel being situated at the opposite ends of the shaft. It is provided that the shaft is welded to the turbine wheel.

As explained at the outset, the turbine wheel of the turbine of a turbocharger is set into rotation by an exhaust gas flow, and drives the compressor via the shaft. The compressor draws in and compresses air. The compressor operates continuously, and is characterized by a small pressure rise and a high volumetric flow rate. The compressed air is conducted into the engine, a large quantity of air entering into the cylinders during the induction stroke due to the increased pressure. As a result, the oxygen content required for the combustion of fuel correspondingly increases, so that more oxygen enters into the combustion chamber of the engine with each intake stroke.

The shaft is welded to the turbine wheel to achieve a secure attachment of the turbine wheel to the shaft, and thus to be able to ensure a connection between the compressor wheel and the turbine wheel. Various welding processes are suited for this purpose.

For example, a friction welding process may be used. Friction welding allows secure joining of components for the same or also different material combinations. This involves a pressure welding process, the heating of the parts to be joined being produced by mechanical friction. The heating is generally produced by a movement between a rotating component and a stationary component, which are joined together under force without filler metal.

As an alternative to the friction welding process, the shaft may also be joined to the turbine wheel with the aid of an electron beam welding process. Due, for example, to the high energy density that is introduced into the welding zone, this process allows the joining of a variety of different materials such as high-melting metals. Electron beam welding allows high welding speeds with extremely deep, narrow weld seams. Warping may be kept very low due to the small weld seam widths and the high degree of parallelism.

Laser beam welding, for example, is also conceivable, thus allowing joining of components at a high welding speed, having a thin, narrow weld seam shape, and with low thermal warping. Laser beam welding is generally carried out without supplying a filler metal.

The turbine wheel is preferably pressed onto the shaft. This procedure is advantageously carried out prior to the welding process. For this purpose, the shaft is provided on the turbine side, for example with a shaft journal which extends in the axial direction and which is pressed into a hole in the turbine wheel. Due to this press fit, a connection between the shaft and the turbine wheel is possible even before the welding, so that the two components subsequently need to be welded together only at the preferably flat contact points. As an alternative, of course, the turbine wheel may be provided with a journal, and the shaft may be provided with a hole at its end face, so that the shaft is pressed into the turbine wheel.

The compressor wheel is advantageously fastened to the shaft with the aid of a nut. For this purpose, the compressor wheel is pushed onto the shaft during assembly, and lastly is clamped at that location with the aid of the nut. A secure connection also between the compressor wheel and the shaft is ensured in this way.

In principle, the bearing components of the bearing cartridge may be preassembled and pushed into the bearing housing starting from the turbine side. This allows delivery of the bearing cartridge with less effort and with low assembly effort for customers.

Further advantageous embodiments are provided in the subclaims directed to the bearing arrangement, which may be analogously transferred to the turbocharger.

BRIEF DESCRIPTION OF THE DRAWING

Exemplary embodiments of the present invention are explained below with reference to a drawing. FIGS. 1 through 4 each show a turbocharger having a bearing arrangement in a longitudinal section.

DETAILED DESCRIPTION

FIG. 1 shows a turbocharger 1 having a bearing arrangement 3. The turbocharger has a compressor wheel 5 and a turbine wheel 7 situated at the opposite ends of a shaft 9 which extends in the axial direction.

Shaft 9 is part of bearing arrangement 3, and is rotatably mounted within a bearing housing 11 which likewise extends axially. Bearing arrangement 3 also includes an anti-friction bearing 13, having two axially adjacent outer bearing rings 15, 17, situated within bearing housing 11. Outer bearing rings 15, 17 are situated at a distance from one another with the aid of a pretensioned spring element 19 situated in between.

Anti-friction bearing 13 also has rolling bodies 21 designed as spheres, which in each case are held in rows in cages 23. Rolling bodies 21 are each guided in rolling body raceways 25, 27 which are integrated into the lateral surface of shaft 9. Rolling body raceways 25, 27 are introduced into the lateral surface in one step directly during manufacture of the shaft. The use of inner bearing rings to be separately installed may thus be dispensed with, since shaft 9 takes over the function of the inner bearing rings.

This reduces the effort during assembly, in which the inner bearing rings must be pushed onto the shaft and pressed onto same. In addition, the axial distance between rolling body raceways 25, 27 always remains the same, so that the shaft play does not change either.

In addition, the sum of the component tolerances may be reduced by dispensing with separate inner bearing rings. The usually additive shape and position defects of the inner bearing rings on shaft 9 may thus be avoided, so that the overall tolerance is smaller.

Entire shaft 9 is manufactured in one piece from a heat-resistant anti-friction bearing steel. The shaft is welded to turbine wheel 7 with the aid of a friction welding process, thus achieving a secure connection between shaft 9 and turbine wheel 7.

In addition, recesses 29, 31 are introduced into shaft 9 as well as into turbine wheel 7. Recesses 29, 31 provide an air volume, so that the thermal conduction from turbine wheel 7 to anti-friction bearing 13 during operation of turbocharger 1 is reduced. Furthermore, the recesses provide space for welding discharge during machining of the shaft.

Shaft 9 is connected to compressor wheel 5 on the side opposite from turbine wheel 7. For this purpose, compressor wheel 5 is pushed onto the shaft and is clamped at that location with the aid of a nut 33.

Grooves 35 for positioning sealing elements 37 are introduced on the outer periphery of shaft 9. Sealing elements 37 seal against leaks and contaminants, on the sides of compressor wheel 5 as well as on the sides of turbine wheel 7.

For assembling the turbocharger, the bearing components may be preassembled and pushed into bearing housing 11 starting from the turbine side. Since the outer diameter of outer bearing rings 15, 17 is slightly smaller than the inner diameter of bearing housing 11, a gap-shaped space 39 results between bearing housing 11 and outer bearing rings 15, 17. Space 39 is acted on by oil via supply hole 41 in bearing housing 11, so that a quenching oil film forms at that location. Supply holes 41, 42 are in communicating connection with grooves 43, 44 on the outer periphery of outer bearing rings 15, 17. In addition, the oil, starting from grooves 43, 44, is distributed into the bearings through splash oil holes 45, 46 connected to grooves 43, and may thus be used for lubrication. An outlet hole 47 is included for drainage.

In addition, an oil separator 49 which operates according to the centrifugal force principle is mounted on shaft 9.

FIG. 2 shows another turbocharger 61 having a bearing arrangement 63. Turbocharger 61 has a compressor wheel 65 and a turbine wheel 67 which are situated at the opposite ends of a shaft 69 which extends in the axial direction. In FIG. 2 as well, the entire shaft 69 is manufactured in one piece from a heat-resistant steel.

Since the function and the individual components of turbocharger 61 in FIG. 2 essentially correspond to those of turbocharger 1 in FIG. 1, at this point reference is made to the detailed description and illustration in FIG. 1, which may be analogously transferred to the discussion below.

In contrast to FIG. 1, turbine wheel 67 is connected to shaft 69 with the aid of electron beam welding. For this purpose, turbine wheel 67 is pressed onto shaft 69. Turbine wheel 67 has a corresponding hole 111 into which shaft journal 113 of the shaft is pressed at the end face of the shaft. Shaft journal 113 is designed as a journal which extends in the axial direction.

Turbine wheel 67 and shaft 69 are subsequently welded only at flat contact surfaces 115 of turbine wheel 67 and of shaft 69 by an electric beam.

Furthermore, shaft 69 is clamped to compressor wheel 65 on the side opposite from turbine wheel 67 with the aid of a nut 93. In addition, an oil separator 109 which operates according to the centrifugal force principle is mounted on shaft 69 on the same side.

FIG. 3 shows another turbocharger 121 having a bearing arrangement 123. Turbocharger 121 likewise has a compressor wheel 125 and a turbine wheel 127 which are situated at the opposite ends of a shaft 129 which extends in the axial direction. Shaft 129 is rotatably mounted within a bearing housing 131 which likewise extends axially.

For this purpose, bearing arrangement 123 has an anti-friction bearing 133, having two axially adjacent outer bearing rings 135, 137, within bearing housing 131. Outer bearing rings 135, 137 are situated at a distance from one another with the aid of a pretensioned spring element 139 situated in between. Anti-friction bearing 133 also has rolling bodies 141 designed as spheres, which in each case are held in rows in cages 143. Rolling bodies 141 are each guided in rolling body raceways 145, 147 which are integrated into the lateral surface of shaft 119 129.

In the installed state, a gap-shaped space 159 which is acted on by oil via two supply holes 161 in bearing housing 131 is provided between the outer diameter of outer bearing rings 135, 137 and bearing housing 131. A quenching oil film forms in the space. Supply holes 161, 162 are in communicating connection with grooves 163, 164 on the outer periphery of outer bearing rings 135, 137. Starting from grooves 163, 164, the oil is additionally distributed into the bearings via splash oil holes 165, 166, and may thus be used for lubrication. An outlet hole 167 is also included for drainage.

The difference in turbocharger 121 from turbochargers 1, 61 previously shown lies in the nature of shaft 129. Shaft 129 is composed of various shaft sections 171, 173, 175. Accordingly, rolling body raceways 145, 147 are introduced into only one shaft section 173. Shaft section 173 correspondingly takes over the function of the inner bearing rings which would otherwise be necessary.

Shaft section 173 is composed of heat-resistant steel, whereas the two axially adjacent shaft sections 171, 175 are made of a less expensive, requirement-specific metallic material.

Shaft sections 171, 173, 175 have axially inwardly extending recesses 176, 177, 178, 179. Inner recesses 176, 177, 178, 179 are designed as cavities which provide an additional air volume. For this reason, they cause a reduction in the thermal conduction from turbine wheel 127 to the bearings. Turbine wheel 127 also has a recess 180 which additionally increases the air volume and thus reduces the thermal conduction.

In the present case, shaft sections 171, 173, 175 are welded together. After shaft sections 171, 173, 175 are welded, shaft section 175 is lastly welded to turbine wheel 127. For this purpose, friction welding is used, as previously described for turbocharger 1 according to FIG. 1.

Lastly, welded shaft sections 171, 173, 175, i.e., shaft 129, is/are welded to turbine wheel 127 at the side of shaft section 175 with the aid of a friction welding process. Turbine wheel 127 also has an inner recess 180, which further decreases the air volume for reducing the thermal conduction from turbine wheel 127 to anti-friction bearing 133 during operation of turbocharger 121.

Compressor wheel 125 is fastened to shaft 129 by pushing the compressor wheel onto shaft 129 on the side of the shaft opposite from turbine wheel 127, and is fastened at that location with the aid of a nut 153. In addition, an oil separator 169 which operates according to the centrifugal force principle is mounted on shaft 129.

FIG. 4 shows another turbocharger 181 having a bearing arrangement 183. Turbocharger 181 has a compressor wheel 185 and a turbine wheel 187 situated at the opposite ends of a shaft 189 which extends in the axial direction. Shaft 189 is rotatably mounted within a bearing housing 191 which likewise extends axially.

Bearing arrangement 183 also includes an anti-friction bearing 193, having two axially adjacent outer bearing rings 195, 197, situated within bearing housing 191; the outer bearing rings, the same as in the preceding figures, are situated at a distance from one another with the aid of a pretensioned spring element 199 situated in between. Anti-friction bearing 193 also has rolling bodies 201 designed as spheres, which in each case are held in rows in cages 203. Rolling bodies 201 are guided in rolling body raceways 205, 207.

Since the function and the individual components of turbocharger 181 in FIG. 4 essentially correspond to those in the exemplary embodiments previously described, at this point reference is made to the detailed description there, which may be analogously transferred to the discussion below.

The same as in FIG. 3, shaft 189 is manufactured from three separate shaft sections 237, 239, 241. Shaft sections 237, 239, 241 are made of various materials, shaft section 239 being made of heat-resistant steel. The two other shaft sections 237, 241 are made of a less expensive metallic material.

Rolling body raceways 205, 207 are accordingly introduced only into shaft section 239, which is made of the steel. Shaft section 239 takes over the function of the inner bearing rings, so that the costs as well as the assembly effort are reduced, and the accuracy is increased.

Shaft section 239 is provided on each end face with two axially extending shaft journals 243, 245. In the installed state, these shaft journals 243, 245 engage with holes 247, 249 which in each case are provided at the axial contact points of shaft sections 237, 241. Shaft journals 243, 245 are appropriately pressed into holes 247, 249 during assembly. Thus, a connection between the components is possible even before the components are welded, which simplifies the subsequent welding process. The individual shaft sections are welded together only at contact surfaces 251, 253 due to the press fit between same.

For fastening to turbine wheel 187, shaft section 241 additionally has a shaft journal 255 on the side opposite from hole 249 which is pressed into hole 257 in turbine wheel 187. After the pressing, the two components, i.e., shaft 189 and turbine wheel 187, are welded to contact points 259. Laser beam welding is used for this purpose, thus allowing joining of components at a high welding speed, having a thin, narrow weld seam shape, and with low thermal warping. Laser beam welding is carried out without supplying a filler metal.

For fastening compressor wheel 185 to shaft 189, the compressor wheel is pushed onto shaft 189 on the side opposite from turbine wheel 187, and is clamped at that location with the aid of a nut 213. A secure connection also between compressor wheel 185 and shaft 189 is ensured in this way. In addition, an oil separator 229 which operates according to the centrifugal force principle is mounted on shaft 189.

LIST OF REFERENCE NUMERALS

-   1 turbocharger -   3 bearing arrangement -   5 compressor wheel -   7 turbine wheel -   9 shaft -   11 bearing housing -   13 anti-friction bearing -   15 outer bearing ring -   17 outer bearing ring -   19 spring element -   21 rolling body -   23 cage -   25 rolling body raceway -   27 rolling body raceway -   29 recess -   31 recess -   33 nut -   35 groove -   37 sealing element -   39 space -   41 supply hole -   42 supply hole -   43 groove -   44 groove -   45 splash oil hole -   46 splash oil hole -   47 outlet hole -   49 oil separator -   61 turbocharger -   63 bearing arrangement -   65 compressor wheel -   67 turbine wheel -   69 shaft -   71 bearing housing -   73 anti-friction bearing -   75 outer bearing ring -   77 outer bearing ring -   79 spring element -   81 rolling body -   83 cage -   85 rolling body raceway -   87 rolling body raceway -   89 recess -   91 recess -   93 nut -   95 groove -   97 sealing element -   99 space -   101 supply hole -   102 supply hole -   103 groove -   104 groove -   105 splash oil hole -   106 splash oil hole -   107 outlet hole -   109 oil separator -   111 hole -   113 shaft journal -   115 contact surface -   121 turbocharger -   123 bearing arrangement -   125 compressor wheel -   127 turbine wheel -   129 shaft -   131 bearing housing -   133 anti-friction bearing -   135 outer bearing ring -   137 outer bearing ring -   139 spring element -   141 rolling body -   143 cage -   145 rolling body raceway -   147 rolling body raceway -   153 nut -   155 groove -   157 sealing element -   159 space -   161 supply hole -   162 supply hole -   163 groove -   164 groove -   165 splash oil hole -   166 splash oil hole -   167 outlet hole -   169 oil separator -   171 shaft section -   173 shaft section -   175 shaft section -   176 recess -   177 recess -   178 recess -   179 recess -   180 recess -   181 turbocharger -   183 bearing arrangement -   185 compressor wheel -   187 turbine wheel -   189 shaft -   191 bearing housing -   193 anti-friction bearing -   195 outer bearing ring -   197 outer bearing ring -   199 spring element -   201 rolling body -   203 cage -   205 rolling body raceway -   207 rolling body raceway -   213 nut -   215 groove -   217 sealing element -   219 space -   221 supply hole -   223 groove -   225 splash oil hole -   227 outlet hole -   229 oil separator -   237 shaft section -   239 shaft section -   241 shaft section -   243 shaft journal -   245 shaft journal -   247 hole -   249 hole -   251 contact surface -   253 contact surface -   255 shaft journal -   257 hole -   259 contact surface 

1-11. (canceled)
 12. A bearing arrangement for a turbocharger, comprising: a bearing housing extending in an axial direction; an anti-friction bearing situated within the bearing housing and having an outer bearing ring and a plurality of rolling bodies; and an axially extending shaft rotatably mounted within the bearing housing, the shaft having a shaft journal on an end-face side for fastening to a turbine wheel.
 13. A bearing arrangement for a turbocharger, comprising: a bearing housing extending in an axial direction; an anti-friction bearing situated within the bearing housing having an outer bearing ring and a plurality of rolling bodies; and an axially extending shaft rotatably mounted within the bearing housing, the shaft including a rolling body raceway for guiding the rolling bodies, the outer bearing ring being guided in the bearing housing by a support ring.
 14. The bearing arrangement as recited in claim 13 wherein the shaft has a shaft journal on an end-face side for fastening to a turbine wheel.
 15. The bearing arrangement as recited in claim 13 wherein the shaft, at least in the area of the rolling body raceway, is made of steel.
 16. The bearing arrangement as recited in claim 13 wherein the shaft is composed of a plurality of axially adjacent shaft sections.
 17. The bearing arrangement as recited in claim 16 wherein the shaft sections are welded together.
 18. The bearing arrangement as recited in claim 13 wherein the shaft includes an inner recess.
 19. The bearing arrangement as recited in claim 13 wherein the outer bearing ring includes a splash oil hole for acting on the anti-friction bearing with lubricant.
 20. The bearing arrangement as recited in claim 13 wherein the shaft includes a plurality of grooves on its outer periphery for positioning sealing elements.
 21. The bearing arrangement as recited in claim 13 wherein the shaft includes an oil separator.
 22. The bearing arrangement as recited in claim 12 wherein the shaft, at least in the area of the rolling body raceway, is made of steel.
 23. The bearing arrangement as recited in claim 12 wherein the shaft is composed of a plurality of axially adjacent shaft sections.
 24. The bearing arrangement as recited in claim 23 wherein the shaft sections are welded together.
 25. The bearing arrangement as recited in claim 12 wherein the shaft includes an inner recess.
 26. The bearing arrangement as recited in claim 12 wherein the outer bearing ring includes a splash oil hole for acting on the anti-friction bearing with lubricant.
 27. The bearing arrangement as recited in claim 12 wherein the shaft includes a plurality of grooves on its outer periphery for positioning sealing elements.
 28. The bearing arrangement as recited in claim 12 wherein the shaft includes an oil separator.
 29. A turbocharger comprising: a compressor wheel; a turbine wheel; and a bearing arrangement as recited in claim 12, the compressor wheel and the turbine wheel being connected via the shaft, and the shaft being welded to the turbine wheel.
 30. A turbocharger comprising: a compressor wheel; a turbine wheel; and a bearing arrangement as recited in claim 13, the compressor wheel and the turbine wheel being connected via the shaft, and the shaft being welded to the turbine wheel. 